1. Field of the Invention
The present invention relates to a cover for a hard disk drive and, more particularly, to a cover constructed using plastic resin and a reinforcing frame to reduce the weight of the hard disk drive cover.
2. Background Art
Hard disk drives are widely used as auxiliary memory devices in computer systems to magnetically record data received as a recording apparatus for magnetically recording data received from an external device, such as a host computer, onto a magnetic recording medium, such as a rotating disk, or reading data that has already been recorded on the disk. The hard disk drive includes a housing that has a base and an attached cover, a mechanism unit having a spindle motor for rotatably mounting the magnetic disk, a head for reading and writing data onto the magnetic disk, an actuator and a voice coil motor for controlling the position of the head, and a circuit unit for performing the electrical process and controlling the overall operation of the mechanism unit.
A hard disk drive has a magnetic head attached at the end of an actuator arm that moves over the hard disk drive to read and write information from the disk. The actuator pivots radially around a shaft on a pivot bearing controlled by a voice coil motor. The disk is rotated at high speed by a spindle motor that is attached to the base of the hard disk drive. While the magnetic head writes or reads data from a predetermined track of the disk, the rotation of the disk causes the magnetic head to be hydrodynamically lifted over the surface of the disk by an air bearing. This hydrodynamic lifting results from the flow of air produced by the rotating disk. This air flow causes the magnetic head to float (fly) above the disk surface and allows the head to move over the disk while maintaining a minute gap. During operation, when the hard disk drive is non-operational or during a power down period, the head of the actuator arm is held in position over a parking zone located on the innermost track on the disk. The purpose of adjusting the actuator arm during periods when the disk is not rotating is to prevent data recorded on the disk from being damaged by the magnetic head slapping against the data surface of the disk.
The hard disk drive also uses a flexible printed circuit board that is connected via a signal cable to the magnetic head and a current terminal of the voice coil motor. The cover of the hard disk drive controls vibrations and other disturbances and protects the inside of the hard disk drive by combining with the base to enclose the hard disk drive. As such, the cover must be have sufficient strength to endure the vibration and disturbances that occur during operation. Another consideration when designing hard disk drive covers is the effect of the cover on the vibrations of the hard disk drive. As the weight of the cover increases, the first harmonic frequency is lowered, thus making it easier for the hard disk drive to reach a resonance condition that would interfere with the operation of the hard disk drive.
Some covers which were developed to improve the operation of the hard disk drive are shown, for example, in U.S. Pat. No. 5,004,207 to Ishikawa entitled Shock Mounting Structure and Magnetic Disk Apparatus, U.S. Pat. No. 4,967,293 to Aruga entitled Multi-Positioner Magnetic Disk Storage Apparatus Having Means for Reducing Mechanical Vibration Interference Between Positioners, U.S. Pat. No. 5,223,996 to Read entitled Combined Shock Mount Frame and Seal for a Rigid Disk Drive, U.S. Pat. No. 5,703,734 to Berberich entitled Disc-Drive Having an Integral Gasket and Continuous Outer Perimeter Shock Bumper, and U.S. Pat. No. 5,535,092 to Bang entitled Apparatus for Reducing Impacts on a Hard Disk Assembly. Contemporary hard disk drive covers are unable to produce a cover with improved vibrational characteristics without requiring expensive machining or special anti-corrosive coatings. Manufacturers have also tried changing the shape of the hard disk drive cover to a more simple design using a press, but that has not led to a difference in the weight of covers and to an improvement in the vibrational characteristics of the hard disk drive.
U.S. Pat. No. 5,025,335 to Stefansky entitled Architecture for 21/2 Inch Diameter Single Disk Drive, mentions a disk drive cover and bottom made out of injection molded plastic that uses a combination of mounting posts and a closed loop, embedded servo tracking system to compensate for the lack of structural rigidity of plastic. The combination of the two adjustments is an improvement of several existing components to compensate for the vibrational characteristics of a plastic housing, rather than a new structural design to improve the vibrational characteristics. The manufacturing of a cover with mounting posts that mate with a printed circuit board increases the cost of manufacturing while reducing the amount of dimensional tolerance that can occur without interfering with the assembly of the disk drive.
Currently, the majority of hard disk drive manufacturers use a die-casting method and aluminum material to produce a cover. Since the aluminum die-casting process uses an injection molding process, pores are formed in the inside that can change the properties of the aluminum material and cause either corrosion or outgasing. To compensate for this deficiency, an E- coating technique is often used after the injection molding process. Not only does the E-coating technique raise the cost of production, but due to out gassing problems manufacturers are trying to find another coating technique. Due to the dimensional imprecision of die-casting, a cover is not ready for use until it has been machined after injection into the die cast. The machining of the cover causes contamination in the inside of the hard disk drive, thus lowering the reliability of the hard disk drive, or in a clean room due to particles that have been machined off of the hard disk drive. Additionally, the required machining process further increases the cost of producing the hard disk drive.
Die-casting using a magnesium material has also been developed to try to improve the vibrational characteristics of the hard disk drive, but magnesium's susceptibility to corrosion has made it problematic to use a cover substantially composed of magnesium. Hard disk drive manufacturers continue to make every possible effort to minimize vibrational characteristic problems while providing the necessary protection to the hard disk drive, but it is still not easy to find a solution to the problem.
I believe it may be possible to provide a hard disk drive that is an improvement over those currently used by manufacturers. A hard disk drive that is made of a light weight material and reinforced with a frame, that does not use the die cast method, that does not require using machining, and that does not require an expensive coating process would decrease the cost of manufacturing the hard disk drives, that does not require the extra steps involved with using mounting posts, that can use plastic of a lower rigidity than otherwise possible if not for the reinforcing frame, that improves the reliability of hard disk drives using plastic covers, and improves the vibrational characteristics of hard disk drives.